1. Field of the Disclosure
The present invention generally relates to novel working fluids uniquely designed for reduced impact on climate change and higher cycle efficiencies, thereby leading to higher overall system efficiencies. In particular, these working fluids are useful in Organic Rankine Cycle (ORC) systems for efficiently converting heat from various heat sources into mechanical energy. The present invention also relates to novel processes for recovering heat from a heat source using ORC systems with a novel working fluid comprising at least about 20 weight percent cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z), trans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-E), or mixtures thereof.
2. Description of Related Art
Previous Rankine Cycle systems have used various working fluids including flammable or combustible working fluids-fluids with relatively high toxicity, fluids with relatively high global warming potentials (GWPs) and fluids with non-zero ozone depletion potentials (ODPs). Industry has been working on replacing ozone-depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). Non-flammable, low toxicity, environmentally sustainable working fluids are highly desirable for Rankine Cycle applications.
It has been found that surprisingly, the novel working fluids of the present invention uniquely provide higher cycle efficiencies in ORC systems that in turn result in higher overall system efficiencies in the power cycle while offering low toxicity, no flammability, zero ODP, and very low GWP.